1. Field of the Invention
The present invention relates to an image forming apparatus for reading and processing an image placed on an original document support and recording an image corresponding to such original image, and in particularly to such image forming apparatus capable of effecting plural different processing modes.
2. Related Background Art
In case of reproducing an original image on a sheet with different processings in different image areas, for example with different image magnifications in different area, such reproduction has been obtained by preparing two copies and obtaining a paste-up from these two copies. However such paste-up is not necessarily beautiful at the contour, and is cumbersome to make for the user.
Situation is also the same in case of taking a part of two original images and reproducing these on a same recording sheet with different processings. Though there have been developed complex color image editing apparatus in order to meet requirements such as inserting a color image into a black-and-white character original or moving a color image within a page, but such apparatus require an editing image memory, are expensive and complex in operation and are therefore unsuitable for the use in usual offices. Also in the usual color copying machines, even if image synthesis is achieved by making a paste-up as explained before, the obtained results are not satisfactory since the black characters may lose their image quality or the junctions of paste-up may become noticeable on the copy.
In the conventional color copying machines, a copy is obtained by separating the original image into three primary colors blue, green and red, and constructing a copy image with complementary color materials of yellow, magenta and cyan, which can be toners or inks employed for example in an electrophotographic process, a thermal transfer process or an ink jet process. However, in any process, since the color image has to be formed by superposing different coloring materials in succession, there inevitably results a color aberration, in the reproduction of fine lines, particularly of black characters, so that such black images appear as the mottles of different colors which are unpleasant for observation. Recently developed digital copying machines are trying to improve the image quality of black characters through new technologies such as black extraction, undercolor removal, edge enhancement etc., but these technologies are not yet complete and may at the same time deteriorate the image quality due to an edge enhancement noise in a halftone image if such halftone image area is included in the original image. In order to avoid such drawback there has been conceived to separate the image into a character image area and a halftone image area and to apply optimum processes respectively to edge area and halftone image area, but such method has never been conducted in complete manner.